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There is currently no evidence that the intervertebral discs (IVDs) can respond positively to exercise in humans. Some authors have argued that IVD metabolism in humans is too slow to respond anabolically to exercise within the human lifespan. Here we show that chronic running exercise in men and women is associated with better IVD composition (hydration and proteoglycan content) and with IVD hypertrophy. Via quantitative assessment of physical activity we further find that accelerations at fast walking and slow running (2 m/s), but not high-impact tasks, lower intensity walking or static positions, correlated to positive IVD characteristics. These findings represent the first evidence in humans that exercise can be beneficial for the IVD and provide support for the notion that specific exercise protocols may improve IVD material properties in the spine. We anticipate that our findings will be a starting point to better define exercise protocols and physical activity profiles for IVD anabolism in humans.
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Scientific RepoRts | 7:45975 | DOI: 10.1038/srep45975
Running exercise strengthens the
intervertebral disc
Daniel L. Belavý1, Matthew J. Quittner1, Nicola Ridgers1, Yuan Ling2, David Connell2,3 &
Timo Rantalainen1
There is currently no evidence that the intervertebral discs (IVDs) can respond positively to exercise in
humans. Some authors have argued that IVD metabolism in humans is too slow to respond anabolically
to exercise within the human lifespan. Here we show that chronic running exercise in men and
women is associated with better IVD composition (hydration and proteoglycan content) and with IVD
hypertrophy. Via quantitative assessment of physical activity we further nd that accelerations at fast
walking and slow running (2 m/s), but not high-impact tasks, lower intensity walking or static positions,
correlated to positive IVD characteristics. These ndings represent the rst evidence in humans that
exercise can be benecial for the IVD and provide support for the notion that specic exercise protocols
may improve IVD material properties in the spine. We anticipate that our ndings will be a starting point
to better dene exercise protocols and physical activity proles for IVD anabolism in humans.
We expect that tissues will adapt to loads placed upon them. Wol1 described the theory of bone adaptation to
loading. In the intervening years, evidence2 has been obtained as to which loading protocols are benecial (oste-
ogenic) for bone. For the intervertebral disc (IVD), little is known about what loading protocols are benecial
for IVD tissue and cause anabolism in humans. We have good knowledge of loading types that are more likely to
damage lumbar IVD tissue in humans, such as exion of the spine with compression3, torsion4 or to damage to
the vertebral end-plate via axial compression3 with subsequent IVD degeneration5. Whilst this information can
inform what activities people should avoid to preserve IVD integrity, it does not inform us on exercise or habitual
physical activity to “strengthen” the IVD. Furthermore, data6 on turnover rates in the IVD, lead to the assumption
that positive adaptation in the mature IVD is unlikely to occur during the normal human lifespan.
Currently we rely on data from animal, IVD cell and IVD tissue models to suggest what kind of loading might
be benecial for the human lumbar IVD. ese models suggest7 that a “likely anabolic loading window” for the
IVD exists: dynamic loading of 0.2–0.8 MPa, generating intra-discal pressures of approximately 0.3–1.2 MPa, at
0.1 to 1 Hz for approximately eight hours a day. Given human data on intra-discal pressures in dierent activities8,
this could9 be extrapolated to suggest that walking or running exercise is likely anabolic for the IVD. Quadrupedal
treadmill running exercise in rodents10,11 can have a positive impact on the rodent IVD. However, directly apply-
ing loading thresholds and protocols from animal models to humans is problematic12 and there is no evidence
yet9 of a benecial eect of exercise on the IVD in humans. We aimed to determine whether benecial eects on
the IVD of exercise can be seen in humans and what loading patterns this might entail.
Our hypothesis was that people who perform regular upright running activity will show better IVD tissue
quality, as shown by higher T2-times13 in their lumbar IVDs, than people who are healthy with no history of spi-
nal disease, but otherwise not physically active. We also hypothesised that there would be a dose-response eect
of dierent volumes of running. Furthermore, to better understand what types of physical activity are likely ben-
ecial for IVD, we explored the relationship between habitual physical activity, as measured by objective accel-
erometry, and IVD characteristics. To reduce the confounding inuence of normal aging on our ndings, and
given evidence9 that IVD maturation is still in process in the third decade of life, we included women and men
aged 25–35 years. It is also not clear how long is required before the IVD might show a measurable adaptation
to exercise, and we therefore recruited only people with a minimum of 5 years history at their current physical
activity level: either no sport (referents), 20–40 km per week running (joggers), or 50 + km per week running
(long-distance runners).
1Deakin University, School of Exercise and Nutrition Sciences, Institute for Physical Activity and Nutrition, 221
Burwood Highway, Burwood, Victoria, 3125, Australia. 2Imaging at Olympic Park, 60 Olympic Boulevard, Melbourne,
Victoria, 3004, Australia. 3Monash University, Wellington Road, Clayton, Victoria, 3168, Australia. Correspondence
and requests for materials should be addressed to D.L.B. (email:
Received: 24 November 2016
accepted: 07 March 2017
Published: 19 April 2017
Scientific RepoRts | 7:45975 | DOI: 10.1038/srep45975
Long-distance runners (Table1) and joggers showed signicantly higher (+ 11.4% and + 9.2% respectively) lum-
bar IVD T2-times than the non-athletic individuals (Fig.1). is eect was also present at all individual vertebral
levels T11/T12 to L5/S1 (Fig.2; upper panel). e eect of running on T2-time was strongest in the IVD nucleus
(Fig.3; + 11% in joggers and + 15% in long-distance runners in the central nuclear region versus + 5% to + 6%
respectively in the anterior annulus and + 5% and + 9% respectively in the posterior annulus). e height of the
IVD relative to that of the vertebral body, an indicator of IVD hypertrophy, was greater in the long-distance run-
ners (Fig.1). When examining individual vertebral levels (Fig.2; lower panel), this eect was present at the lower
No spor t
(20–40 km)
(50 k + )
Number of males (of
total N) 11 of 24 13 of 30 11 of 25
Body mass (kg) 73.9(17.8) 68.2(11.1) 63.5(10.2)*
Age (yrs) 29.3(3.7) 30.2(3.2) 30.1(3.9)
Height (cm) 173.2(8.7) 173.6(9.7) 170.3(9.2)
Weekday sitting time
(hrs) 9.7(2.1) 6.3(2.8)‡ 6.4(2.8)‡
participation (yrs) - 8.8(4.2) 7.6(3.9)
participation (hrs/
- 4.9(2.2) 8.6(4.3)
Exercise distance
(km/wk) - 28.0(6.7) 66.6(19.5)
IVD volume (cm3) 9.5(2.3) 10.1(3.4) 10.1(3.3)
IVD average area
(mm2)250.2(41.2) 263.6(60.8) 263.0(58.9)
IVD height (mm) 7.1(0.7) 7.3(1.1) 7.5(1.0)
IVD anteroposterior
width (mm) 25.6(2.4) 26.4(3.5) 25.9(3.4)
distance (mm) 34.2(2.0) 34.1(2.9) 34.0(2.8)
Prrmann grade 2.3(0.39) 2.2(0.39) 2.1(0.39)
Erector spinae size
(cm2)14.3(3.3) 14.4(5.0) 14.1(4.8)
Lumbar multidus
size (cm2)4.7(1.1) 4.4(1.6) 4.1(1.6)
Psoas size (cm2) 9.1(2.8) 10.1(4.2) 9.6(4.0)
lumborum size
3.5(1.1) 3.4(1.7) 3.1(1.6)
Table 1. Participant characteristics, intervertebral disc characteristics and lumbar muscle morphology.
Values of continuous variables are mean(SD). *p < 0.05; p < 0.01; p < 0.001 and indicate signicance of
dierence to the non-sporting group. e proportion of females:males did not dier across groups (χ
2 = 0.01,
p = 0.99). ree participants were of Asian descent (one female 20–40 km runner, one male 20–40 km runner,
one male 50 + km runner) and the remaining participants were Caucasian. Prrmann grade was averaged from
all lumbar discs. Areas of erector spinae, multidus, psoas and quadratus lumborum muscles were averaged
from le and right sides of the body and all lumbar levels.
Figure 1. Runners have more hydrated (le) and hypertrophied (right) lumbar IVDs. Values are
mean(SD) averaged across all lumbar discs. Le panel: Higher T2-times indicate13 better IVD hydration and
glycosaminoglycan content. Right panel: IVD height relative to vertebral body height. *p < 0.05; p < 0.01 and
indicate signicance of dierence to the non-sporting group.
Scientific RepoRts | 7:45975 | DOI: 10.1038/srep45975
lumbar vertebral levels L3/L4 to L5/S1. Lumbar muscle size did not dier between groups (Table1). e eect of
running exercise was consistent for both genders, with the gender × group interaction not reaching signicance
(p > 0.18). e long-distance group typically showed greater dierences in IVD parameters to the non-sporting
group than the jogging group. However, there were no statistically signicant dierences between the two run-
ning groups.
Total physical activity levels, as measured by objective accelerometry, were not related to IVD characteristics
(Fig.4). Rather, IVD nucleus T2-time was most strongly associated with accelerations in the range 0.44 and 0.59 g
mean amplitude deviation (MAD; Fig.5). Additional accelerometry data collected under dierent exercise con-
ditions in ten individuals (SupplementaryTable1) showed that ambulation at 2 m/s fell inside this 0.44 and 0.59 g
MAD range. Walking at 1.5 m/s or slower fell below this range and running at 2.5 m/s or faster and jumping were
above this range.
Before the rst interventional studies to dene exercise regimes for improving bone characteristics were per-
formed in the 1990s, an important step was the nding of dierences in bone density between dierent athletic
populations14. is built on prior animal studies and helped to show that exercise may well result in anabolic
adaptation of bone. In this vein, the current study builds on prior work in animal, cell and tissue explant models7
and provides the rst ever cross-sectional evidence in humans that exercise may well favourably impact the IVD.
Our main nding was that long-distance runners and joggers showed better hydration and glycosaminogly-
can levels (higher lumbar IVD T2-times13) than the non-athletic individuals. is is consistent with ndings of
an anabolic response in the IVD in quadrupedal animals10,11 to running. e nding is also consistent with the
notion, developed on the basis of cell, tissue explant and animal models7,15, of a “likely anabolic window” for
IVD loading. e eect of running in humans on IVD composition was most obvious in the IVD nucleus where
intra-discal pressure increases with applied axial load are constrained by the ring-formed annular bres16.
Beyond the compositional dierences, there was evidence of IVD hypertrophy in the long-distance runners.
e height of the IVD relative to that of the vertebral body, which serves as an internal control for body size, was
greater in the long-distance runners. is extends on ndings17 from monozygotic twins that IVDs were margin-
ally, but not signicantly, larger in those twins that were at least 8 kg heavier than their twin pair and presumably
experienced greater habitual spinal loading. Hypertrophy of the IVD may well be an adaptation to habitual load-
ing in runners. Similar to hypertrophic responses seen in muscle due to resistance training18, this suggests that
tissue adaptation will occur in the IVD with exercise. Overall our ndings provide support for the hypothesis that
an adaptive, anabolic and hypertrophic response is possible in the human IVD with exercise.
e current study also provides some guidance on what kinds of loading protocols may be better for the IVD.
To understand what kinds of physical activity in humans might be the drivers of an anabolic response in the IVD,
we examined the physical activity patterns of our collective via objective accelerometry. Total physical activity
levels were not related to positive adaptations in the IVD, rather accelerations in a specic range. e strongest
association to higher IVD T2-times were seen between 0.44 and 0.59 g mean amplitude deviation. is ts with
the idea from animal, tissue and cell models7 of a “likely anabolic window” for the IVD. To better understand
what kinds of activities generate these acceleration magnitudes, we collected additional accelerometry data under
dierent conditions. Walking or slow running at 2 m/s fell inside this range with slower walking falling below this
range. Fast running and high-impact jumping activities were above this range. is is in line with the notion that
high-impact loading is considered7,19 to be detrimental to the IVD and vertebral end-plate. Dynamic IVD load-
ing of 0.2–0.8 MPa, generating intra-discal pressures of approximately 0.3–1.2 MPa, is thought7 to be an optimal
loading magnitude for the IVD. Based upon data on in vivo intradiscal pressures8, activities such as walking and
running, but not liing a 20 kg load or lying down, fall into this loading magnitude window. is corresponds
well to our observations here of the impact of exercise in athletes. We also noted that sedentary activities were
unrelated to IVD characteristics. In light of prior work, the results of our study suggest that, in comparison to
other locomotor activity, fast walking or slow running may provide the strongest anabolic stimulus for adaptation
in the IVD in humans.
Whilst the long-distance running group showed consistently better IVD properties than the jogging group,
there were no statistically signicant dierences between the two. Also, there was no relationship between the
IVD characteristics and physical activity in the 0.7 to 0.9 g MAD range where the physical activity associated with
running was most evident (SupplementaryFigure1). is indicates a ceiling eect of exercise for the IVD was
approached for both volume of upright axial spine loading and intensity. A ceiling eect in relation to exercise
has been observed for muscle hypertrophy20 and bone adaptation to exercise21. It is possible that high volume or
intensity running is not required for a benecial adaptation in the IVD.
In the wider population, it is the lower lumbar IVDs that are most commonly aected by degeneration22.
Furthermore, repetitive loading of the spine is considered23 to be a contributory factor to the development of IVD
degeneration. Despite repetitive loading of the spine during running, the exercise groups of the current study
did not show any detrimental eects at these lower lumbar segments. In contrast, the long-distance runners and
joggers showed evidence of better IVD hydration and glycosaminoglycan content in the lower lumbar spine than
those that did not perform sport. Furthermore, the evidence for IVD hypertrophy subsequent to habitual run-
ning was strongest at the lower lumbar levels. Our data show that repetitive axial loading of the spine under body
weight during running in otherwise healthy people may well be benecial for the lower lumbar IVDs.
It is important to consider some of the limitations of the current study. We performed a cross-sectional study
as a rst step to examine whether certain types of exercise might be benecial for the IVD in humans. In this
design it is not possible to completely rule out other confounding factors. We showed, for example, that lumbar
muscle size was similar in all groups and this indicates that muscle adaptation per se is not the likely cause of
Scientific RepoRts | 7:45975 | DOI: 10.1038/srep45975
Figure 3. e impact of running on the disc is strongest in the nucleus. Top: 3D plot of mean T2-time across
entire IVD volume. Bottom: At the mid-line (sagittal) portion of the IVD the impact of running can be seen to
be greatest in the central, nuclear, portion of the IVD. *p < 0.05; p < 0.01 versus non-sporting group. Greater
T2-times indicate13 better IVD hydration and glycosaminoglycan content.
Figure 2. Eect of running is also present at lowest lumbar vertebral levels: T2-time (top) and IVD height
relative to vertebral body height (bottom). Values are mean(SD) at each vertebral level. *p < 0.05; p < 0.01;
p < 0.001 and indicate signicance of dierence to the non-sporting group. VB: vertebral body.
Scientific RepoRts | 7:45975 | DOI: 10.1038/srep45975
dierences in IVD characteristics in our populations. However, we cannot rule out other factors such as dif-
ferences in muscle function, dierences in nutrition, systemic hormonal (e.g. growth factors, cytokines, stress
hormones) dierences, or other indirect eects. To denitively determine that the mechanical loading from spe-
cic exercise forms result in positive adaptations in the IVD, to determine mechanisms of action, and delineate
exercise guidelines for strengthening the IVD, randomised controlled exercise trials are necessary.
at an optimal loading level and pattern for the IVD exists makes sense from a tissue homeostatis perspec-
tive. Given that tissues such as bone21 and muscle18 have optimal loading conditions for an anabolic response, for
the IVD we should expect it to be no dierent. Our ndings support the perspective that, when loaded appropri-
ately, anabolic IVD adaptation can occur in humans and that this can occur on time frame for it to be meaningful
within the human lifespan.
Evidence that the IVD will respond anabolically in humans to certain types of loading may have public health
implications. Spinal pain consistently presents one of the greatest costs to developed societies for disability and
lost productivity, including when increased death rates in other diseases are accounted for24. IVD degeneration
and herniation is one important contributing factor to spinal pain. Similar to understanding the impact of specic
exercise in other disease constellations, for example in type II diabetes25, knowing that the IVD can respond to
certain kinds of loading, and understanding what kinds of loading are optimal, will result in better exercise guide-
lines for the prevention and management of spinal pain.
Figure 4. Total physical activity levels were unrelated to IVD characteristics. Empty symbols = males, lled
symbols = females. Individual values for each subject shown. ere was no correlation between total physical
activity levels and T2-time in the intervertebral disc (IVD) nuclear region.
Figure 5. Specic loading levels impact the IVD nucleus T2-time. Values are mean(95% CI) correlation
between IVD nucleus T2-time and count data in each mean amplitude deviation bin. e strongest association
to higher IVD T2-times were seen between 0.44 and 0.59 g. is corresponds to fast walking and slow jogging
(see Results and SupplementaryTable1).
Scientific RepoRts | 7:45975 | DOI: 10.1038/srep45975
Ethical approval and subjects. e study was approved by the Deakin University Faculty of Health,
Medicine, Nursing & Behavioural Sciences human ethics advisory group. All subjects gave their informed writ-
ten consent prior to participation in the study. All methods were performed in accordance with the relevant
guidelines and regulations. To reduce the impact of normal ageing on the ndings, only individuals aged 25 to
35 years of age were included. Exclusion criteria included current spinal pain, history of spinal surgery, history of
traumatic injury to the spine, known scoliosis for which prior medical consultation was sought, current or prior
smoker, known claustrophobia and possible pregnancy. We recruited three groups of people with distinct loading
histories: joggers (20–40 km per week), long-distance runners (50+ km per week) and non-sporting referents.
To be included in the jogging group, subjects needed to have been running 20–40 km per week for a minimum
of the last 5 years and perform no other sport or exercise type more than once per week. Long-distance runners
were required to have performed at least 50 km per week for a minimum of the last 5 years and, with the exception
of resistance exercise for muscle hypertrophy (muscle hypertrophy training is a common training component
of long-distance runners), no other sport or exercise type more than once per week. Included in the “no-sport”
group were individuals who performed no regular sport or exercise in the last ve years, currently performed
less than 150 minutes of moderate activity (dened as activity that “causes an individual to breathe harder than
normal”) per week26, and walked less than 15 min to or from their place of work. A total of 79 participants were
included in the study (Table1).
Testing and scanning protocol. Participants were instructed not to perform any exercise on the day of
their scan. Due to normal diurnal variation in IVD water content, all testing was performed aer midday. Upon
arriving at the radiology facility, participants were required to sit for a minimum of 20 minutes prior to entering
the scanner with participants sitting for a mean(SD) of 44(16) minutes which did not dier between groups
(p > 0.19). During this time participants completed questionnaires detailing their gender, type of physical activity,
body height, and average sitting duration Monday to Friday. e runners also reported distance run per week,
time run per week and number of years of participation.
To quantify IVD T2-time and morphology, a spin-echo multi-echo sequences on a 3T Phillips Ingenia scanner
(Amsterdam, Netherlands) was used with spinal coils to collect images at 8 echo times (15.75, 36.75, 57.75, 78.75,
99.75, 120.75, 141.75 and 162.75 ms) from 13 sagittal anatomical slices each (thickness 3 mm; interslice distance:
1.5 mm; repetition time: 2000 ms, eld of view: 281 × 281 mm, image resolution: 0.366 mm per pixel) encom-
passing the entire lower spine from le to right. For radiological categorisation of IVD degeneration (Prrmann
grade), a sagittal plane T2-weighted sequence (15 slices, slice thickness: 3 mm, interslice distance: 1.5 mm, repeti-
tion time: 2600 ms, echo time: 70 ms, eld of view: 357 mm × 357 mm, resolution: 0.532 mm per pixel) was taken.
To quantify muscle morphology, a paraxial T1-weighted scan (repetition time: 800 ms, echo time: 9 ms, slice
thickness: 4 mm, interslice distance: 2 mm, eld of view: 258.68 × 258.68 mm, image resolution: 0.270 mm per
pixel) with ve groups of three slices each positioned at each vertebral body L1 to L5 and oriented to the vertebral
end-plates was performed. Data were exported for further oine processing.
Aer scanning, subjects were given a hip-mounted ActiGraph model GT3X+ (Pensacola, FL). Participants
were instructed to wear the ActiGraph during all waking hours except during water-based activities (e.g. swim-
ming and bathing) for eight consecutive days. Acceleration data were collected at 100 Hz with a ±6 g range and
12 bit analog to digital conversion.
Oine image processing and analysis. To ensure blinding of the examiner to oine image measure-
ments, each subject was assigned a random numeric code (obtained from A radiologist deter-
mined the Prrmann grade of each lumbar IVD (Table1) on sagittal T2-weighted images. Seven individuals had
a supernumerary lumbar vertebral segment and the additional IVD (designated L6/S1) in these subjects was not
included in analyses.
ImageJ 1.38x ( was used to perform all quantitative MRI measures. In the sagittal
spin-echo multi-echo images every IVD from T11/T12 to L5/S1 was measured. Aer segmenting the IVD, a
custom written ImageJ plugin (“ROI Analyzer”; was used to rotate the
region of interest to the horizontal and measure area, height, width and signal intensity of the IVD in its entirety
as well as in ve subregions from the anterior to posterior aspect of the disc. T2-time was calculated via linear t
to the natural logarithm of the image intensity in each of the eight MR echos. Similar parameters were generated
for each of the ve disc subregions and interpolated across the width of the IVD to generate the 3D plots pre-
sented in Fig.3. Volume of each IVD in each subject was calculated by linear interpolation of the area data from
all slices. e image number where each spinous process was best visible was noted. e vertebral body was also
segmented and vertebral body height measured in a similar fashion in order to calculate the ratio of IVD height to
vertebral body height, as a normalised indicator of IVD hypertrophy. e data from each lumbar IVD were also
averaged. With the exception of IVD volume (Table1), data averaged from the three images around the spinous
process were used in analysis.
In each of the paraxial T1-weighted images, area of the lumbar multidus, erector spinae, psoas and quadratus
lumborum were measured bilaterally from L1 to L5 as in prior work27. e muscle area averaged from all lumbar
levels was used in analysis.
3D accelerometry analysis. Once participants returned the Actigraph, raw data were downloaded from
the device and analysed with a custom-written Matlab script (R2015b, Mathworks, Inc., Natick, MA, USA).
Resultant acceleration was calculated from the 3-dimensional data, and used in all further analyses. No smooth-
ing was applied on the recorded signal.
Scientific RepoRts | 7:45975 | DOI: 10.1038/srep45975
Mean amplitude deviation ( =
1, where n = number of data points in an epoch, i = data point
index, x = resultant acceleration,
= mean of the epoch, and vertical bars signify taking the absolute value)28 was
calculated from the resultant acceleration in non-overlapping 5 s epochs in 24 h segments starting at 6 am local
time for all of the recorded days. e 5 s epoch mean MADs were divided into 98 logarithmically equidistant bins
(= histogram) from 0 g to 2.5 g. Non-wear time was dened as any hours with standard deviation less than 0.024 g,
and any days with less than 10 h of total wear-time were excluded from analysis. Data from individuals with 3
days of sucient wear-time were included. 70 individuals completed the Actigraph data collection and were
included in the analysis. Two individuals from the no-sport group, six from the jogging group and one from the
long-distance running group did not complete this data collection. On average, 7.6 days of complete data were
available per participant (similar across all three groups, p = 0.9). e mean of all included days is reported.
Additional sub-study: which activities generate what accelerations? To relate MAD to physical
activities, 10 individuals performed a graded treadmill test at speeds of 0.5 m/s, 1 m/s, 1.5 m/s, 2 m/s, 2.5 m/s,
3.0 m/s and 3.5 m/s whilst wearing a hip-mounted ActiGraph. At each speed, 70 seconds of data were collected
and the data from the 11 second onwards was used for further analysis. Participants also performed 10 consec-
utive jumps maintaining the knee and hip at near full extension (similar to hopping on one leg, but bilaterally).
Statistical analyses. An alpha-level of 0.05 was taken for statistical signicance. For continuous variables,
T-tests were performed comparing the long-distance and jogging groups to the non-sport referent group. Primary
analysis evaluated IVD T2-time (composition measure) and IVD height to vertebral body height ratio (hypertrophy
measure) averaged across all lumbar levels. Data from individual vertebral levels were also evaluated. Dierence in
response between males and females was evaluated via two-way analysis of variance for ‘group’ and ‘gender’. For com-
paring physical activity to IVD characteristics, the correlation and 95% condence interval was calculated between
number of counts for each subject in the MAD bin and the average lumbar IVD T2-time in the nucleus (central
subregion). e mean and 95% condence interval of the MADs in each of the physical activities of the sub-study
were calculated. e “R” statistical environment (version 2.10.1, was used for all analyses.
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Scientific RepoRts | 7:45975 | DOI: 10.1038/srep45975
We thank the subjects for participating in the study. We also thank the sta at Imaging at Olympic Park for their
support in implementing the study. is project was supported by internal institutional funding from Deakin
University School of Exercise and Nutrition Sciences (reference number ‘Belavy 2014–2017 ).
Author Contributions
D.L.B.: Contributed conception and design of the experiments, image analysis, statistical analysis, interpretation
of the data, draing the article. M.Q.: contributed subject recruitment, data collection, image analysis, approved
manuscript. N.R.: contributed to conception and design of the experiments, analysis of actigraph data, revision of
the manuscript, approved manuscript. Y.L.: contributed radiological assessment of images, approved manuscript.
D.C.: contributed to conception and design of the experiments, support with data collection, interpretation of
the data, approved manuscript. T.R . : contributed to conception and design of the experiments, data analysis,
statistical analysis, draing manuscript, approved manuscript.
Additional Information
Supplementary information accompanies this paper at
Competing Interests: e authors declare no competing nancial interests.
How to cite this article: Belavý, D. L. et al. Running exercise strengthens the intervertebral disc. Sci. Rep. 7,
45975; doi: 10.1038/srep45975 (2017).
Publisher's note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and
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© e Author(s) 2017
... These loading patterns lead to diurnal changes in tissue compressive strain, resulting in corresponding changes in the osmotic environment of the cells. Such diurnal patterns may be altered due to a sedentary lifestyle, obesity or rotating shift work, contributing to the risks of developing diseases such as osteoarthritis and IVD degeneration 12,13,16,17 . Cartilage and IVDs possess intrinsic circadian clocks that drive rhythmic expression of tissuespecific genes and become dampened and out of phase in aging mice [18][19][20][21] . ...
... A notable aspect of clock network synchrony is its apparent redundancy, with multiple cues signaling timing to specific tissues in a synergistic manner. Regular exercise is thought to be beneficial for the maintenance of skeletal muscle, joint and IVD as well as reducing severity of osteoarthritis symptoms 17,40 . However, no critical studies have directly evaluated the importance of time-of-day. ...
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Daily rhythms in mammalian behaviour and physiology are generated by a multi-oscillator circadian system entrained through environmental cues (e.g. light and feeding). The presence of tissue niche-dependent physiological time cues has been proposed, allowing tissues the ability of circadian phase adjustment based on local signals. However, to date, such stimuli have remained elusive. Here we show that daily patterns of mechanical loading and associated osmotic challenge within physiological ranges reset circadian clock phase and amplitude in cartilage and intervertebral disc tissues in vivo and in tissue explant cultures. Hyperosmolarity (but not hypo-osmolarity) resets clocks in young and ageing skeletal tissues and induce genome-wide expression of rhythmic genes in cells. Mechanistically, RNAseq and biochemical analysis revealed the PLD2-mTORC2-AKT-GSK3β axis as a convergent pathway for both in vivo loading and hyperosmolarity-induced clock changes. These results reveal diurnal patterns of mechanical loading and consequent daily oscillations in osmolarity as a bona fide tissue niche-specific time cue to maintain skeletal circadian rhythms in sync.
... Spine MRI. Intervertebral disc composition [48], vertebral fat fraction [49] and paraspinal muscle size and composition [50] will be assessed using a 3T MRI scanner with the following sequences: 1) T2 sag spin-echo multi-echo, 2) Sag DIXON, 3) Axial DIXON, 4) Axial PD and 5) T2-weighted Sag. Radiological assessment will also be performed for the presence of radiological evidence of degenerative changes: facet joint osteoarthritis, pars defects and spondylolisthesis, disc herniation, spinal stenosis, osteophytes, Modic changes and disc degeneration (Pfirrmann grade �3; [51]). ...
... As part of standard practice, MR image data is checked visually by the MR-operator and investigator team member during scanning and scans repeated once if, for example, movement or other artefacts impact the images collected. MR images are measured manually by trained staff using established protocols [48,49,90] to obtain the numerical outcomes of interest. The remaining numerical data (e.g. ...
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In patients presenting with low back pain (LBP), once specific causes are excluded (fracture, infection, inflammatory arthritis, cancer, cauda equina and radiculopathy) many clinicians pose a diagnosis of non-specific LBP. Accordingly, current management of non-specific LBP is generic. There is a need for a classification of non-specific LBP that is both data- and evidence-based assessing multi-dimensional pain-related factors in a large sample size. The "PRedictive Evidence Driven Intelligent Classification Tool for Low Back Pain" (PREDICT-LBP) project is a prospective cross-sectional study which will compare 300 women and men with non-specific LBP (aged 18-55 years) with 100 matched referents without a history of LBP. Participants will be recruited from the general public and local medical facilities. Data will be collected on spinal tissue (intervertebral disc composition and morphology, vertebral fat fraction and paraspinal muscle size and composition via magnetic resonance imaging [MRI]), central nervous system adaptation (pain thresholds, temporal summation of pain, brain resting state functional connectivity, structural connectivity and regional volumes via MRI), psychosocial factors (e.g. depression, anxiety) and other musculoskeletal pain symptoms. Dimensionality reduction, cluster validation and fuzzy c-means clustering methods, classification models, and relevant sensitivity analyses, will classify non-specific LBP patients into sub-groups. This project represents a first personalised diagnostic approach to non-specific LBP, with potential for widespread uptake in clinical practice. This project will provide evidence to support clinical trials assessing specific treatments approaches for potential subgroups of patients with non-specific LBP. The classification tool may lead to better patient outcomes and reduction in economic costs.
... Also, we gave a range of repetitions (a minimum and a maximum number of exercise repetition) so that the patient could adjust the exercise, and so his training, on his pain and sensations. Fast walking and running were selected: there is strong evidence in literature that this practice is associated with better hydration and proteoglycan content in the intervertebral disc (IVD) (14). Disc damage in sports like weightlifting, where there is a huge axial loading on the spine, can be present, and as the time passes it can lead to disc degeneration (15). ...
... Disc damage in sports like weightlifting, where there is a huge axial loading on the spine, can be present, and as the time passes it can lead to disc degeneration (15). Running and fast walking have an effect on the muscles, too: they strengthen the back muscles by increasing their activation through an isometric contraction, and this can be also used for the prevention of LBP (14,16). Additionally, we recommend the TRX exercises, such as: TRX hip drop, back row, T-spine rotation, standing side bands, which promote the balance, strength and flexibility develop, especially in the athletes. ...
... All tissues of the IVD and synovial joints are dynamic structures that exist in balance between catabolic and anabolic pathways. Chondrocytes, nucleus pulposus cells and annulus fibrosus cells are continually remodelling the ECM in response to extracellular stimuli, especially load-bearing forces 36,87 , which probably contributes to the positive efficacy of physical exercise for IDD 112 and OA 113 although other mechanisms are also at work 112,114 . Depending on the frequency and magnitude of load-bearing forces, nucleus pulposus cells and annulus fibrosus cells upregulate catabolic factors, such as matrix metalloproteases (MMPs) and a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS) proteases, or anabolic factors such as collagen and aggrecan 36 . ...
... All tissues of the IVD and synovial joints are dynamic structures that exist in balance between catabolic and anabolic pathways. Chondrocytes, nucleus pulposus cells and annulus fibrosus cells are continually remodelling the ECM in response to extracellular stimuli, especially load-bearing forces 36,87 , which probably contributes to the positive efficacy of physical exercise for IDD 112 and OA 113 although other mechanisms are also at work 112,114 . Depending on the frequency and magnitude of load-bearing forces, nucleus pulposus cells and annulus fibrosus cells upregulate catabolic factors, such as matrix metalloproteases (MMPs) and a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS) proteases, or anabolic factors such as collagen and aggrecan 36 . ...
Intervertebral disc degeneration (IDD) and osteoarthritis (OA) affecting the facet joint of the spine are biomechanically interdependent, typically occur in tandem, and have considerable epidemiological and pathophysiological overlap. Historically, the distinctions between these degenerative diseases have been emphasized. Therefore, research in the two fields often occurs independently without adequate consideration of the co-dependence of the two sites, which reside within the same functional spinal unit. Emerging evidence from animal models of spine degeneration highlight the interdependence of IDD and facet joint OA, warranting a review of the parallels between these two degenerative phenomena for the benefit of both clinicians and research scientists. This Review discusses the pathophysiological aspects of IDD and OA, with an emphasis on tissue, cellular and molecular pathways of degeneration. Although the intervertebral disc and synovial facet joint are biologically distinct structures that are amenable to reductive scientific consideration, substantial overlap exists between the molecular pathways and processes of degeneration (including cartilage destruction, extracellular matrix degeneration and osteophyte formation) that occur at these sites. Thus, researchers, clinicians, advocates and policy-makers should consider viewing the burden and management of spinal degeneration holistically as part of the OA disease continuum.
... MPa on the disc, which produces an intradiscal pressure of 0.3-1.2 MPa, is considered the optimal amount of load, and walking and running fall just within this load amplitude window (Belavý et al., 2017), while different types of PA will exert different types of loads on the intervertebral disc. Not only that, but intervertebral discs rely heavily on the diffusion of nutrient exchange through the endplates, and it has been found that different loads can affect the rate at which small solutes penetrate into the discs (Belavý et al., 2016). ...
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Objective: Previous studies are insufficient to confirm a causal association between physical activity (PA) and low back pain (LBP), intervertebral disc degeneration (IDD), and sciatica. The present study used a two-sample Mendelian randomization (MR) analysis method to demonstrate whether or not there was a causal connection. Methods: First, four PA phenotypes were selected [accelerometer-based PA (average acceleration), accelerometer-based PA (acceleration fraction >425 mg), self-reported moderate-to-vigorous PA, and self-reported vigorous PA], setting thresholds for single nucleotide polymorphisms (SNPs) significantly concerned with PA p < 5 × 10 ⁻⁸ , linkage disequilibrium (LD) r ² < 0.01, genetic distance >5,000 kb, and F-value >10. SNPs associated with the outcome and confounding factors were then excluded using the PhenoScanncer database. Finally, after coordinating the genetic instruments from genome-wide association studies (GWAS) effect alleles for exposure and outcomes, multiplicative random effects inverse variance weighting (IVW), MR-Egger, weighted median method (WMM), and weighted mode method were used to assess exposure-outcome causality and perform sensitivity analysis on the estimated results. Results: The current study’s IVW findings revealed proof of a causal connection between PA and LBP. While there was a positive causal tie between accelerometer-based PA (acceleration fraction >425 mg) and LBP [OR: 1.818, 95% CI:1.129–2.926, p = 0.012], there was a negative causal link between accelerometer-based PA (average acceleration) and LBP [OR: 0.945, 95% CI: 0.909–0.984, p = 0.005]. However causal relationship between PA and IDD or sciatica was not found. Conclusion: Increasing average PA but needing to avoid high-intensity PA may be an effective means of preventing low back pain. Although PA is not directly causally related to disc degeneration and sciatica, it can act through indirect pathways.
... In this same study, hypertrophy in long-distance running was identified in the IVD in contrast with the jogging group. 164 These comparisons confirm that the loading characteristics and conditions are critical for maintaining the disc or leading to injury and degeneration. Understanding and investigating different types of loading should remain an ongoing focus in IVD research, as this information can be integrated into the current protocols to evaluate DDD, regenerative approaches, and refine the exercise guidelines for pain management and prevention. ...
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Low back pain is the leading cause of disability, producing a substantial socio-economic burden on healthcare systems worldwide. Intervertebral disc (IVD) degeneration is a primary cause of lower back pain, and while regenerative therapies aimed at full functional recovery of the disc have been developed in recent years, no commercially available, approved devices or therapies for the regeneration of the IVD currently exist. In the development of these new approaches, numerous models for mechanical stimulation and preclinical assessment, including in vitro cell studies using microfluidics, ex vivo organ studies coupled with bioreactors and mechanical testing rigs, and in vivo testing in a variety of large and small animals, have emerged. These approaches have provided different capabilities, certainly improving the preclinical evaluation of these regenerative therapies, but challenges within the research environment, and compromises relating to non-representative mechanical stimulation and unrealistic test conditions, remain to be resolved. In this review, insights into the ideal characteristics of a disc model for the testing of IVD regenerative approaches are first assessed. Key learnings from in vivo, ex vivo, and in vitro IVD models under mechanical loading stimulation to date are presented alongside the merits and limitations of each model based on the physiological resemblance to the human IVD environment (biological and mechanical) as well as the possible feedback and output measurements for each approach. When moving from simplified in vitro models to ex vivo and in vivo approaches, the complexity increases resulting in less controllable models but providing a better representation of the physiological environment. Although cost, time, and ethical constraints are dependent on each approach, they escalate with the model complexity. These constraints are discussed and weighted as part of the characteristics of each model.
... Additionally, other researchers have shown that the effect of hydrostatic pressure on IVD response is dose dependent, with higher forces eliciting a catabolic response [37]. These data suggest dynamic, cyclical, loading (such as during running) may be anabolic for IVDs, which is supported by cross-sectional studies in humans [38,39]. In our model, Panx3 KO mice forced to run develop histological features of IDD while there was weak evidence for this in WT mice. ...
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Pannexin 3 (Panx3) is a glycoprotein that forms mechanosensitive channels expressed in chondrocytes and annulus fibrosus cells of the intervertebral disc (IVD). Evidence suggests Panx3 plays contrasting roles in traumatic versus aging osteoarthritis (OA) and intervertebral disc degeneration (IDD). However, whether its deletion influences the response of joint tissue to mechanical stress is unknown. The purpose of this study was to determine if Panx3 deletion in mice causes increased knee joint OA and IDD after forced treadmill running. Male and female wildtype (WT) and Panx3 knockout (KO) mice were randomized to either a no exercise group (sedentary; SED) or daily forced treadmill running (forced exercise; FEX) from 24 to 30 weeks of age. Knee cartilage, tibial subchondral bone and IVD histopathology were evaluated by histology. Both male and female Panx3 KO mice developed larger superficial defects of the tibial cartilage after forced treadmill running compared to SED WT mice. Additionally, both male and female Panx3 KO mice developed a sclerotic secondary ossification center of the tibia with running. In the lower lumbar spine, both male and female Panx3 KO mice developed histopathological features of IDD after running compared to SED WT mice. Clinical Significance: These findings suggest that the combination of deleting Panx3 and forced treadmill running induces OA and causes histopathological changes associated with degeneration of the IVDs in mice.
... The run doesn't seem non-harmful for cartilage [28,29] and these findings align with what was reported by other authors [30][31][32]. Similarly to the results of this review, in the mouse models was found that forced treadmill running on elderly mice led to moderate beneficial tribology and lubricative properties and preventing cartilage degeneration [33]. ...
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Molecular composition and structural adaptation are changes in the cartilage tissue after different stimuli. Sports activities with different loads at different angles, speeds, and intensities can modify the molecular composition of the articular cartilage, hence it is crucial to understand the molecular adaptations and structural modifications generated by sports practice and this review aims to synthesize the current evidence on this topic. A systematic search until July 2022 was performed on the database Medline, Pubmed, Scopus, and Web of Science with a collection of 62,198. After the screening process, the included articles were analyzed narratively. Thirty-one studies have been included in the analysis. From the results emerged that running, swimming, ballet and handball were not correlated with detrimental structural or molecular cartilage adaptation; instead, soccer, volleyball, basketball, weightlifting, climbing, and rowing showed signs of cartilage alteration and molecular adaptation that could be early predictive degeneration's signs. From the included studies it came to light that the regions more interested in morphological cartilage changes were the knee in athletes from different disciplines. In conclusion, different sports induce different cartilage modifications both at a molecular and structural level and it is important to know the risks correlated to sports to implement preventive strategies.
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The classification of non-specific chronic low back pain (CLBP) according to multidimensional data could guide clinical management; yet recent systematic reviews show this has not been attempted. This was a prospective cross-sectional study of participants with CLBP (n = 21) and age-, sex- and height-matched pain-free controls (n = 21). Nervous system, lumbar spinal tissue and psychosocial factors were collected. Dimensionality reduction was followed by fuzzy c-means clustering to determine sub-groups. Machine learning models (Support Vector Machine, k-Nearest Neighbour, Naïve Bayes and Random Forest) were used to determine the accuracy of classification to sub-groups. The primary analysis showed that four factors (cognitive function, depressive symptoms, general self-efficacy and anxiety symptoms) and two clusters (normal versus impaired psychosocial profiles) optimally classified participants. The error rates in classification models ranged from 4.2 to 14.2% when only CLBP patients were considered and increased to 24.2 to 37.5% when pain-free controls were added. This data-driven pilot study classified participants with CLBP into sub-groups, primarily based on psychosocial factors. This contributes to the literature as it was the first study to evaluate data-driven machine learning CLBP classification based on nervous system, lumbar spinal tissue and psychosocial factors. Future studies with larger sample sizes should validate these findings.
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Background Osteoporosis and postmenopausal bone loss pose a huge social and economic burden worldwide. Regular exercise and physical activity are effective interventions for maximizing or maintaining peak bone mass and preventing bone loss in the elderly; however, most recommendations are addressed to the general public and lack specific indications for girls and women, the segment of the population most at risk for developing osteoporosis. Objective The aim of this overview of systematic reviews and meta-analyses was to summarize current evidence for the effects of exercise and physical activity interventions on bone status in girls and women, and to explore whether specific exercise programs exist for improving or maintaining bone mass or bone strength in females. Methods The PubMed, EMBASE, PEDro, and Cochrane Library databases were searched from January 2009, updated to 22 June 2015, using the following groups of search terms: (i) ‘physical activity’ and ‘exercise’; and (ii) ‘bone’, ‘bone health’, ‘bone strength’, ‘bone structure’, ‘bone metabolism’, ‘bone turnover’, and ‘bone biomarkers’. Searches and screening were limited to systematic reviews or meta-analyses of studies in females and published in English. Our final analysis included 12 articles that met the inclusion criteria. Results Combined-impact exercise protocols (impact exercise with resistance training) are the best choice to preserve/improve bone mineral density in pre- and postmenopausal women. Peak bone mass in young girls can be improved with short bouts of school-based high-impact plyometric exercise programs. Whole-body vibration exercises have no beneficial effects on bone in postmenopausal or elderly women. Conclusions and Implications Lifelong exercise, specific for age, is an effective way to sustain bone health in girls and women.
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To better understand what kinds of sports and exercise could be beneficial for the intervertebral disc (IVD), we performed a review to synthesise the literature on IVD adaptation with loading and exercise. The state of the literature did not permit a systematic review; therefore, we performed a narrative review. The majority of the available data come from cell or whole-disc loading models and animal exercise models. However, some studies have examined the impact of specific sports on IVD degeneration in humans and acute exercise on disc size. Based on the data available in the literature, loading types that are likely beneficial to the IVD are dynamic, axial, at slow to moderate movement speeds, and of a magnitude experienced in walking and jogging. Static loading, torsional loading, flexion with compression, rapid loading, high-impact loading and explosive tasks are likely detrimental for the IVD. Reduced physical activity and disuse appear to be detrimental for the IVD. We also consider the impact of genetics and the likelihood of a 'critical period' for the effect of exercise in IVD development. The current review summarises the literature to increase awareness amongst exercise, rehabilitation and ergonomic professionals regarding IVD health and provides recommendations on future directions in research.
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Using data from 16 published reports, the authors correlated macroscopic disc degeneration grades with age, sex, and spine level In 600 lumbar Intervertebral discs from 273 cadavers (ages: 0-96 years). Male discs were more degenerated than female discs at most ages; significantly so In the second, fifth, sixth, and seventh decades. On average, L4-L5 and L3-L4 level discs showed more degeneration than discs at other lumbar levels. These macroscopic findings corroborate radio-graphic data from epldemlologlc studies. The calculations suggest that higher mechanical stress, perhaps combined with longer nutritional pathways, may be responsible for the earlier degeneration of male discs.
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Accelerometers are increasingly used for objective assessment of physical activity. However, because of lack of the proprietary analysis algorithms, direct comparisons between accelerometer brands are difficult. In this study, we propose and evaluate open source methods for commensurate assessment of raw accelerometer data irrespective of the brand. Twenty-one participants carried simultaneously three different tri-axial accelerometers on their waist during five different sedentary activities and five different intensity levels of bipedal movement from slow walking to running. Several time and frequency domain traits were calculated from the measured raw data, and their performance in classifying the activities was compared. Of the several traits, the mean amplitude deviation (MAD) provided consistently the best performance in separating the sedentary activities and different speeds of bipedal movement from each other. Most importantly, the universal cut-off limits based on MAD classified sedentary activities and different intensity levels of walking and running equally well for all three accelerometer brands and reached at least 97% sensitivity and specificity in each case. Irrespective of the accelerometer brand, a simply calculable MAD with universal cut-off limits provides a universal method to evaluate physical activity and sedentary behaviour using raw accelerometer data. A broader application of the present approach is expected to render different accelerometer studies directly comparable with each other.
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Background: Measuring disease and injury burden in populations requires a composite metric that captures both premature mortality and the prevalence and severity of ill-health. The 1990 Global Burden of Disease study proposed disability-adjusted life years (DALYs) to measure disease burden. No comprehensive update of disease burden worldwide incorporating a systematic reassessment of disease and injury-specific epidemiology has been done since the 1990 study. We aimed to calculate disease burden worldwide and for 21 regions for 1990, 2005, and 2010 with methods to enable meaningful comparisons over time. Methods: We calculated DALYs as the sum of years of life lost (YLLs) and years lived with disability (YLDs). DALYs were calculated for 291 causes, 20 age groups, both sexes, and for 187 countries, and aggregated to regional and global estimates of disease burden for three points in time with strictly comparable definitions and methods. YLLs were calculated from age-sex-country-time-specific estimates of mortality by cause, with death by standardised lost life expectancy at each age. YLDs were calculated as prevalence of 1160 disabling sequelae, by age, sex, and cause, and weighted by new disability weights for each health state. Neither YLLs nor YLDs were age-weighted or discounted. Uncertainty around cause-specific DALYs was calculated incorporating uncertainty in levels of all-cause mortality, cause-specific mortality, prevalence, and disability weights. Findings: Global DALYs remained stable from 1990 (2·503 billion) to 2010 (2·490 billion). Crude DALYs per 1000 decreased by 23% (472 per 1000 to 361 per 1000). An important shift has occurred in DALY composition with the contribution of deaths and disability among children (younger than 5 years of age) declining from 41% of global DALYs in 1990 to 25% in 2010. YLLs typically account for about half of disease burden in more developed regions (high-income Asia Pacific, western Europe, high-income North America, and Australasia), rising to over 80% of DALYs in sub-Saharan Africa. In 1990, 47% of DALYs worldwide were from communicable, maternal, neonatal, and nutritional disorders, 43% from non-communicable diseases, and 10% from injuries. By 2010, this had shifted to 35%, 54%, and 11%, respectively. Ischaemic heart disease was the leading cause of DALYs worldwide in 2010 (up from fourth rank in 1990, increasing by 29%), followed by lower respiratory infections (top rank in 1990; 44% decline in DALYs), stroke (fifth in 1990; 19% increase), diarrhoeal diseases (second in 1990; 51% decrease), and HIV/AIDS (33rd in 1990; 351% increase). Major depressive disorder increased from 15th to 11th rank (37% increase) and road injury from 12th to 10th rank (34% increase). Substantial heterogeneity exists in rankings of leading causes of disease burden among regions. Interpretation: Global disease burden has continued to shift away from communicable to non-communicable diseases and from premature death to years lived with disability. In sub-Saharan Africa, however, many communicable, maternal, neonatal, and nutritional disorders remain the dominant causes of disease burden. The rising burden from mental and behavioural disorders, musculoskeletal disorders, and diabetes will impose new challenges on health systems. Regional heterogeneity highlights the importance of understanding local burden of disease and setting goals and targets for the post-2015 agenda taking such patterns into account. Because of improved definitions, methods, and data, these results for 1990 and 2010 supersede all previously published Global Burden of Disease results. Funding: Bill & Melinda Gates Foundation.
1. Compression forces are mainly absorbed by the vertebral body. The nucleus pulposus, being liquid, is incompressible. The tense annulus bulges very little. On compression the vertebral end-plate bulges and blood is forced out of the cancellous bone of the vertebral body into the perivertebral sinuses. This appears to be the normal energy-dissipating mechanism on compression. 2. The normal disc is very resistant to compression. The nucleus pulposus does not alter in shape or position on compression or flexion. It plays no active part in producing a disc prolapse. On compression the vertebral body always breaks before the normal disc gives way. The vertebral end-plate bulges and then breaks, leading to a vertical fracture. If the nucleus pulposus has lost its turgor there is abnormal mobility between the vertebral bodies. On very gentle compression or flexion movement the annulus protrudes on the concave aspect–not on the convex side as has been supposed. 3. Disc prolapse consists primarily of annulus; it occurs only if the nucleus pulposus has lost its turgor. It then occurs very easily as the annulus now bulges like a flat tyre. 4. I have never succeeded in producing rupture of normal spinal ligaments by hyperextension or hyperflexion. Before rupture occurs the bone sustains a compression fracture. On the other hand horizontal shear, and particularly rotation forces, can easily cause ligamentous rupture and dislocation. 5. A combination of rotation and compression can produce almost every variety of spinal injury. In the cervical region subluxation with spontaneous reduction can be easily produced by rotation. If disc turgor is impaired this may occur with an intact anterior longitudinal ligament and explains those cases of tetraplegia without radiological changes or a torn anterior longitudinal ligament. The anterior longitudinal ligament can easily be ruptured by a rotation force and in my experience the so-called hyperextension and hyperflexion injuries are really rotation injuries. 6. Hyperflexion of the cervical spine or upper thoracic spine is an anatomical impossibility. In all spinal dislocations a body fracture may or may not occur with the dislocation, depending upon the degree of associated compression. In general, rotation forces produce dislocations, whereas compression forces produce fractures.
Sixty-one lumbar intervertebral joints were compressed while wedged to simulate hyperflexion. Twenty-six of the joints failed by posterior disc prolapse. The results show that slightly degenerated discs at lower lumbar levels from subjects aged between 40 and 50 years are most susceptible to prolapse.
SUMMARY In order to stimulate further adaptation toward specific training goals, progressive resistance training (RT) protocols are necessary. The optimal characteristics of strength-specific programs include the use of concentric (CON), eccentric (ECC), and isometric muscle actions and the performance of bilateral and unilateral single- and multiple-joint exercises. In addition, it is recommended that strength programs sequence exercises to optimize the preservation of exercise intensity (large before small muscle group exercises, multiple-joint exercises before single-joint exercises, and higher-intensity before lower-intensity exercises). For novice (untrained individuals with no RT experience or who have not trained for several years) training, it is recommended that loads correspond to a repetition range of an 8-12 repetition maximum (RM). For intermediate (individuals with approximately 6 months of consistent RT experience) to advanced (individuals with years of RT experience) training, it is recommended that individuals use a wider loading range from 1 to 12 RM in a periodized fashion with eventual emphasis on heavy loading (1-6 RM) using 3- to 5-min rest periods between sets performed at a moderate contraction velocity (1-2 s CON; 1-2 s ECC). When training at a specific RM load, it is recommended that 2-10% increase in load be applied when the individual can perform the current workload for one to two repetitions over the desired number. The recommendation for training frequency is 2-3 dIwkj1 for novice training, 3-4 dIwkj1 for intermediate training, and 4-5 dIwkj1 for advanced training. Similar program designs are recom- mended for hypertrophy training with respect to exercise selection and frequency. For loading, it is recommended that loads corresponding to 1-12 RM be used in periodized fashion with emphasis on the 6-12 RM zone using 1- to 2-min rest periods between sets at a moderate velocity. Higher volume, multiple-set programs are recommended for maximizing hypertrophy. Progression in power training entails two general loading strategies: 1) strength training and 2) use of light loads (0-60% of 1 RM for lower body exercises; 30-60% of 1 RM for upper body exercises) performed at a fast contraction velocity with 3-5 min of rest between sets for multiple sets per exercise (three to five sets). It is also recommended that emphasis be placed on multiple-joint exercises especially those involving the total body. For local muscular endurance training, it is recommended that light to moderate loads (40-60% of 1 RM) be performed for high repetitions (915) using short rest periods (G90 s). In the interpretation of this position stand as with prior ones, recommendations should be applied in context and should be contingent upon an individual's target goals, physical capacity, and training